/*
 * Cache.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.util;

/**
 * The <code>Cache</code> interface is used to represent a cache
 * that will store key value pairs. The cache exposes only several
 * methods to ensure that implementations can focus on performance
 * concerns rather than how to manage the cached values.
 *
 * @author Niall Gallagher
 */
public interface Cache<T> {

    /**
     * This method is used to determine if the cache is empty. This
     * is done by checking if there are any elements in the cache.
     * If anything has been cached this will return false.
     *
     * @return this returns true if the cache is empty
     */
    boolean isEmpty();

    /**
     * This method is used to insert a key value mapping in to the
     * cache. The value can later be retrieved or removed from the
     * cache if desired. If the value associated with the key is
     * null then nothing is stored within the cache.
     *
     * @param key   this is the key to cache the provided value to
     * @param value this is the value that is to be cached
     */
    void cache(Object key, T value);

    /**
     * This is used to exclusively take the value mapped to the
     * specified key from the cache. Invoking this is effectively
     * removing the value from the cache.
     *
     * @param key this is the key to acquire the cache value with
     * @return this returns the value mapped to the specified key
     */
    T take(Object key);

    /**
     * This method is used to get the value from the cache that is
     * mapped to the specified key. If there is no value mapped to
     * the specified key then this method will return a null.
     *
     * @param key this is the key to acquire the cache value with
     * @return this returns the value mapped to the specified key
     */
    T fetch(Object key);

    /**
     * This is used to determine whether the specified key exists
     * with in the cache. Typically this can be done using the
     * fetch method, which will acquire the object.
     *
     * @param key this is the key to check within this segment
     * @return true if the specified key is within the cache
     */
    boolean contains(Object key);
}